Cracking process



Oct. l, 1946. c. H. o. BERG Y 2,408,600

CRACKING PROCESS` Filedsept` 22, 194s Separator' 'Hopper' 24d v .i FZ/e/anda/r v Burner/ J0 l l eacof i 5Z...l

33 30 F/e @as j Regeneration 6 Chamber 5a@ 35 Affe 22 Off/Fae i9 f dv.QF f 4 l j fr v Cl v lNvENToR.

- CZyoEEO. 559e,

BY WMM bed type.

Patented oct. 1, 1946 GRAC'KING PROCESS ClydeH. 0. Berg, Long Beach,Calif., assignor to Union Oil Company of California, Los Angeles,Calif., a corporation of California- Application September 22, 1943,Serialv No. 503,345

7 Claims. (Cl. 196-52) This invention relates to the catalyticconversion of hydrocarbons, and especially to the cracking of petroleumfractions in the presence of a moving stream of granular catalyst.

Catalytic cracking processes are known wherein the crackingy iscarried-out in the presence of moving catalysts, and these processes areamong the most efcient in use today. The. known processes of this natureare of two different types, namely (l) the fluid type, and (2) themoving Each of these has its own advantages and disadvantages. V

The fluid type process employs a powdered or dust-type catalyst which isblown through the reaction zone by a stream of feed vapors, and then isseparated from the vaporous conversion products, and regenerated bybeing blown through a regeneration zone by a stream of air.

The moving bed type process employs a gran ular or bead type catalyst,which moves downward as a solid. bed through a reaction zone throughwhich a countercurrent stream of feed vapors is passed, and then isseparated from the vaporous conversion products, mechanically conveyedto the top of a regeneration zoneV through which it moves downward in asolid bed through which air for regeneration is passed, the regeneratedcatalystv being separated and mechanically conveyed to the top of thereaction zone for reuse. f

The fluid processvhas some advantages over the moving bed process insimplicity of construction of reactor and regenerator chambers, but hasdisadvantages in di'culty of separation of the catalyst from the gasstreams, with attendant catalyst loss, and diiiiculty of control ofregeneration temperatures. The moving `bed process has the advantageover the fluid process in lower catalyst loss, more easily controllableregeneration temperatures and less. difficult catalyst separation, butthe two mechanical Vconveyor systems involved are very expensive tob-uild and maintain and must be adjusted frequently vto balance thereaction system against the regeneration system.

A process has now been discovered which has rthe advantages of both ofthe above systems withform of 'the prorcessis illustrated in the"attached figure, wherein a catalytic reactor is positioned above a'catalyst regeneration chamber, and a continuous solid' stream ofgranulated catalyst flows down' through both chambers-l,v the catalystbeing carried back to the t'opl of the reactor by suspension in agaseous stream of vaporized feed.

Referring to the iigure, vaporized and pre'- heated hydrocarbon feed isintroduced through line Iv and control valve 2. In mixing section 3 thisfeed' gas is mixedwtih catalyst from line 4, and carries this catalystin suspension upward through line 5 and into separator 6. Here the gasis separated from thev catalyst and passes-out through line l.' Thecatalyst drops through line 3| into hopper 8; and thence downward in asolid moving, bed' or stream through sealing leg 9 into reactory I0'.

In reactor I0 the catalyst is heatedl byindirect heat exchange with hotcombustion gases passing through tube 26 and obtained byr burning fuelwith air in burnerV H'. The hydrocarbon vapors from line 'l' areintroduced near the bottom of the reactor through lines I2and 2-4 andvalves l3` and 3l', and are subjected tocountercurrent contact with theflowing' catalyst. The product vapors' leave the" top of the reactorlthrough line I4 and valve 3A, which are kept' clear ofV catalyst bypassing the' catalyst down through tubes I5, which extend. below outlett4 and thus provide a disengaging'space.

The used catalyst drops from the lower party of reactor 1'0 throughsealing leg 30" into regeneration chamber |61 where` it is regeneratedby con'- tact with air entering through line 35 and valve 36, and` iscooled by indirect heat exchange'with a c-ooling medium entering throughline I1 and leaving through linev I8.A The regeneration flue gases leavethrough line 25, and the regenerated catalyst leaves the bottom of thechamber through conical' section I9: containing baiile 20', dropsthrough line 2 I' containing shut-off Valve 22 and orifice 23 into lineY4, and repeats 'its cycle. Catalyst lmay be withdrawn from thef'systemthrough line 28 and valve 29 or added to' the hopper 8 through line 2l.

There are many advantages in the above" described process overconventional processes. The equipment is simplev to' construct andoperate. There are no" complicated mechanical conveyor systems,v andcatalyst separation is simple and eflicient with the preferred granularcatalysts. There is no necessity` for balancing of the flow of catalystthrough the reactor.l against the flow throughthe regeneration. chamber,since both flows arey part ofi a single continuous' cycle. Im

3 troducing hot feed into line I appears to give a desirable preliminarycracking in line 5.

Separator 6 may be a conventional cyclone separator, and the reactor,regeneration chamber and auxiliary equipment are of simple design andfabricated from common materials of construction. N o baflies, packing,etc. are neces? sary in themain body of the hopper, reactor, orregeneration chamber, although they may be employed if desired. Theregeneration chamber may be of multi-tube or multi-coil design withmultiple air inlets and flue gas outlets to provide very closetemperature control if desired. Similarly, the reactor may be equippedwith multiple heaters, and multiple feed inlets and outlets if desired,to control contact time and temperature to provide either isothermaloperation or operation with the desired temperature gradient. Multipletubes may also be used in place of the single line shown. Baffie 20 ismerely a circular shield located centrally in conical section i9 toprevent the ow through the central portion of the regeneration chamberfrom exceeding materially the ow through the outer portion. If desired,any catalyst fines leaving with the gases in lines 1, I4 and 39 may beremoved by Cyclones, Cottrell precipitators, settlers or the like. Anysmall loss of catalyst may be compensated for by the addition of newcatalyst through line 21. The effectiveness of sealing legs such aslines 9, 30 and Z! may be improved by injecting a sealing gas such assteam, flue gas, carbon dioxide, nitrogen, and the like into the side ofthe lines at some point .or points not too close to either end. This isillustrated in the ligure by the addition of steam into line 30 throughline 40 and valve 4I.

In a second method of operation, hydrogen or a light hydrocarbon gas maybe fed through line y hydrocarbon feed may be introduced through valve33 and lines 32 and I2. The gas leaving separator 6 may be withdrawnthrough lines 1 and 39 and valves 31 andv 38, or part or all of it'maybe introduced into reactor I9 with the feed, through lines 1, 24 and I2,and valves 31 and I3. In this type of operation it may be most effectiveto add considerable heat to the gas during its passage through line `24,or to heat the mixture in line I2.

Although the above methods are preferred,

a third method may be employed, wherein concurrent flow of feed vaporsand catalyst is employed in reactor I0. This may be done by closingvalves 34 and 31 and forcing the feed vapors entering line i to passdown through separator 6, hopper 8 and reactor I0, leaving through lineI2. In this method it is notl necessary that line 9 be a sealing leg. Infact hopper 8 may be incorporated as an integral part of reactor I0,with no intervening constriction.

The above processes may be employed for many types of hydrocarbonconversion, including cracking, polymerization, reforming and rening.include processes wherein there is a scission of carbon-to-carbon bondsof the feed hydrocarbons, such as in conventional cracking of various Bythe term cracking it is intended to l petroleum fractions, as well asdealkylation, de-

the term reforming it is intended to include processes involvingprimarily a change in structure without substantial change in molecularWeight, such as hydrogenation and dehydrogenation, aromatization,isomerization, and the like. By refining is meant4 the conversion ofsmall amounts of undesirable hydrocarbons or contaminants to lessobjectionable forms, as in the polymerization of color and gum unstableolens, dioleflns, and the like, conversion of sulfur, oxygen, andnitrogen-containing contaminants in hydrocarbon stocks to easilyremovable forms such as HzS, H2O, NH3 and the like. I

The hydrocarbon feed stocks may be various petroleum fractions, such asnatural or cracked gases, natural, crude or cracked gasolines,kerosenes, gas oils, lubricating oils, extracts, or other productsobtained by conversion or extraction of such stocks; or similarfractions from coal tar, shale and the like. These may be converted bythe appropriate treating processes of the previous paragraph to stable,high-octane gasolines, specific olefms, aromatics, naphthenes, orisopara'ins, or other desired products.

As examples of the above processes, a gas oil fraction from petroleummay be vaporized and heated to about 800 F., the vapors being introducedinto line I. These vapors pick up catalyst from line 4 and carry thecatalyst upward to separator 6 from which the catalyst flows through thehopper, reactor, and regenerator as previously described. The feedvapors from separator 6 are introduced at the bottom of reactor I0 asindicated, being further preheated in line 24 if desired. An auxiliarygas such as hydrogen, a light hydrocarbon or an inert gas may beintroduced into this stream through line 39 and valve 38, if desired,and this gas may be preheated to supply any additional heat desired. Forexample, a, propane or butane or lighter fraction from the product maybe preheated to 1100 F. and introduced into 39 so as to increase thetemperature of the mixture in line 24 to 900 F. to 1000o F. The mixturemay then be subjected to cracking in the presence of the catalyst inreactor I0 at substantially atmospheric pressure. The product may bewithdrawn through line I4, and fractionally distilled to obtain a gasfraction, partof which is recycled through line 39, a gasoline of goodantidetonation charactervistics, a gas oil which may be vaporizedandrecycled to line I, and a residuum suitable as fuel oil.

A gasoline or naphtha fraction may be reformed by a similar process. Byoperating at a pressure of l0 or more atmospheres and using hydrogenVthrough line 39 rather than a light hydrocarbon, a product of higheraromatic hydrocarbon content and lower olefln content may usually beobtained.

In another mode of operation, flue gases at a temperature of 2000 F. to4000 F. may be added through line 39 to give a preliminary thermalcracking at temperatures between about 1000 F. and 2000 F. to thehydrocarbons from line 1. Diluents such as inert gases, recycledfractions, etc., may be added through line 32 to control the temperatureof the subsequent catalytic reaction in reactor I0.

The above 4operations may also-be used for the dehydrogenation ofbutanes to butenes, and the further dehydrogenation to butadiene, inwhich vinto line I instead of feed stock vapors in orderV to carry theregenerated catalyst up through yline 5, while the feed stock isintroduced through line 32. It is also possible to employ the concurrentilow method described earlier, `wherein sealing leg 9 is eliminated andthe vapors in line '5 `are forced down through the reactor.v This methodis particularly effective when treatingv a gasoline to polymerizeunstable gum-formingoleflns, since the polymers formed may condense andbe swept out of the bottom'ofy the reactor. other ,operations, however,the countercurrentfcontacting is preferred.

As catalysts for the cracking and reforming operations alumina,silica-alumina rcombinations and group VI metal oxides such aschromiumand molybdenum oxides, especially when employed with a supportor carrier such as alumina or other metal oxide gel and the like, aresuitable. For hydrogenation operations, oxides of metals having atomicnumbers between 22 and 30 Tand especially cobalt, nickel and copper,andcombinations of these with chromium, molybdenum', titanium, Vanadium,and the-like, as mixtures and as compounds such as chromites,molybd-ates, etc., are suitable. .These may also be employedy oncarriers. For refining cracked gasolines, `active clays, bauxite,magnesia, fullers earth, andgvarious oxide gels are suitable. Theselatter are also suitable carriers for the more active catalystsmentioned above. The invention is of course not limited to the use ofthe specific catalysts named.

The catalysts should be granular, preferably about 4 to20 mesh in size,although sizes between about 1 and 60 mesh may be employed in manyinstances, and where special bailling is employed in the reactorkandcooler to permit countercurrent flow of the gases without suspensionof the catalyst therein, smaller sizes down to about 100 mesh may beemployed.

Y The reaction is preferably carried out in the vapor phase, asindicated, although liquid phase operation may also be employed, such asby introducing a liquid feed through line I4, allowing it to flow downthrough the catalyst bed in reactor Il), and withdrawing the productthrough line I2. This would necessitate maintenance of a liquid level ator just above line I2, and provision of means such as a trap forpreventing loss of liquid product through line 3U.

The temperatures employed for cracking are generally high, in the rangeof about 800 F. to 2000 F. Many of the reforming operations such asdehydrogenation and aromatization also require high temperatures in thisrange, but isomerization and hydrogenation for example may be carried onat lower temperatures, down to about atmospheric. The pressures involvedmay range from about atmospheric up to 100 atmospheres or more, althoughfor vapor phase operation pressures below about atmospheres arepreferable'. Operation of both the reaction and regeneration processesat substantially the same pressure is a heatingy uid in reaction chamberIQ.

preferred. but pressure. differences up te .1.0 at mospheres ,or `moremay be tolerated .by the use ofproperly ydesignen sealing :legs 'es thepres,-

-sure differential is increased, the-.eieeney ef the seaune ieg must beincreased. esfor exemple -bv lengthening .the leg. er using more Sealinggas.

The `relative amounts of feed stock, auxiliary gas `and vcatalystemployed will vary with the resuits desired. `-As an example however2.applying to the aromatization of a crude gasoline ,fraction at 1.000 F.and 10 atmospheres pressure, thelfeed may be introduced at a rate Qf l(liquid) volume per volume of catalyst @in reactor. Ill) per hour,hydrogen may be .employed in e retin ef 3000 cubic feet per barrel of(liquid) feed, and the catalyst may be circulated at a rate -of about0.5 volume per hour. The catalyst flow rate is regulated largely. by thesizeof the 4.orifice 23, `Feed,

auxiliary ses. and catalyst flow4 rates between about one-tenth to tentimes the above rates may be employed, yanderen Wider limits may be usedin some instances. Y l l Outstanding features of the process of thisin.- vention yas mentioned previously,;are its simplicity Vand the useof a granular catalyst circulated by suspension in a flowing gaseousstream, followed by gravitational downward flow in a solid stream. Nodifficulty has been experienced in carrying granules of the above sizesup through line 5'. For example, granules of v12 to 30 mesh have beenlifted over 3 5 feet through a ,1% inch pipe VVline at a rate of about400 pounds. per hour by a gas stream of about rmvpounds per hour.

In a variation of the process of `this invention, the regenerationchamber vI6 is placed above reactor I, with sealing leg 30 between andsealing leg 2| below as usual. Non-combustible inert gas with or withoutsome air may then be introduced into line I, the obvious modificationsin flow being employed. ,y

In any of the above systems it is apparentthat there are vmanyvariations which may be 1employed.` Fory example the cooling fluidemployed in `regeneration chamber l 6 may also -be employedas This wouldnecessarily involve a gaseous fluid, or possibly a system of flowingsolids such as the catalyst iiow system, but would preferably be aliquid such as a molten salt. When the cooling fluid i-s not also usedin the reactor as a heating iiuid, water or steam could be used as thecooling medium, or the feed stock, steam, or auxiliary gas employedcould be preheated by using it as the cooling medium.

Although the process of this invention has been described primarily as ahydrocarbon conversion process, it may also be employed for shale oileduction, oxidation, and like processes. dation, oxygen may besubstituted for at least a part of the auxiliary gas in the abovesystems. For shale oil eduction, fresh granulated shale is added throughline 21. In hopper 8 it is diluted with a controlled amount of hotrecycled spent shale from line Sand separator 6, and passes into reactorI0 used as an eduction chamber. In reactor I0 itis heated, as by uegases in tube 26, and subjected to stripping gas such as steam enteringthrough line I2, the product leaving line I4. The stripping gas may alsoenter line I4, and the product leave through line I2 if desired toprovide for simpler recovery of liquid products. The educted shale,which generally contains some carbonaceous residue even though eductedat temperatures of 900? F. to 1500 F. is burned in chamber I6, the heatbeing absorbed by the stripping For oxigas which enters through line I1,leaving line I8, 'and entering chamber I0 through line l2 or I4 asdescribed. Part of this preheated stripping gas may also be charged intoline l to carry the desired amount of recycled spent shale through line5, or flue gases from line 26 may be used. The spent shale not recycledis Iwithdrawn through line 28. Its heat content may be employed forsteam generation or the like. The stripping gas may also be flue gas,nitrogen and the like although hydrogen and light hydrocarbons from theproduct leaving chamber l are preferred.

Other modifications of the processes of this invention which would occurto one skilled in the art are to be considered within the scope of thisinvention as defined in the following claims:

I claim: 1. A process for the catalytic conversion of hy- 'drocarbonswhich comprises ilowing a granulated catalyst downwardly by gravitythrough successive zones of reaction and regeneration, introducinghydrocarbons into said reaction Zone and maintaining an elevatedconversion temperature therein while said hydrocarbons flow through saidreaction zone countercurrently to said flowing catalyst, regeneratingsaid catalyst in said regeneration zone, withdrawing regeneratedcatalyst from said regeneration Zone, suspending said withdrawn catalystin a suspension gas to thereby lift said catalyst and pass it to aseparating zone, separating said catalyst from said suspension gas insaid separating zone, passing said separated catalyst to said reactionzone, and introducing said separated suspension gas into said reactionzone with said hydrocarbons.

2. A process according to claim 1 in which the suspension gas compriseshydrocarbon feed,

` p V3. A process according to claim l in which the said reaction zone,regenerating said catalyst in said regeneration zone, withdrawingregenerated catalyst from said regeneration zone, suspending thewithdrawn catalyst in a suspension gas comprising hydrocarbon feed tothereby lift said catalyst and pass it to a separating zone, separatingsaid catalyst from said 'suspension gas in said separating zone, passingthe separated catalyst to said reaction zone, adding to said separatedsuspension gas ue gases having a temperature between about 2000 F. and4000" F. so as to give a preliminary thermal cracking `to saidhydrocarbon feed at a temperature between about 1000 F. and 2000 F., andpassing the resulting gaseous mixture through said reaction zonecountercurrently to said flowing catalyst.

6. A process according to claim 5 in which the catalyst granules arebetween about 4 and 20 mesh in size.

7. An apparatus for the catalytic conversion of hydrocarbons whichcomprises a reactor and a regeneration chamber so connected and arrangedthat granulated catalyst may ilow by gravity successively through saidreactor and regeneration chamber, means for introducing catalyst intosaid reactor, means for introducing a gaseous mixture into said reactorto pass countercurrently to said catalyst, means for maintaining anelevated ternperature in said reactor, means for regenerating saidcatalyst in said regeneration chamber, means located near the bottom ofsaid regeneration chamber for controlling the rate of flow ofcatalystrthroughsaid reactor and said regeneration chamber, outlet meansfor removing said catalyst from said regeneration chamber, separatingmeans positioned above said reactor for separating gases from catalyst,means connecting said outlet' means with said separating means, meansfor introducing a suspension gas into said connesting means to therebysuspend said catalyst in

